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<meta name="description" content="This variation on the LinkLabelDraggingTool extension restricts link labels to stay on the link&#39;s route while the user is dragging it."/> 
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<title>Draggable Link Labels That Stay On Path</title>
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          <h1 class="mb-0 p-1 ">GoJS</h1>
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    <!-- * * * * * * * * * * * * * -->
    <!-- Start of GoJS sample code -->
    
    <script src="../release/go.js"></script>
    <div class="p-4 w-full">
<script src="LinkLabelOnPathDraggingTool.js"></script>
<script id="code">
  function init() {
    if (window.goSamples) goSamples();  // init for these samples -- you don't need to call this
    var $ = go.GraphObject.make;

    myDiagram =
      $(go.Diagram, "myDiagramDiv", // the ID of the DIV HTML element
        {
          layout: $(go.ForceDirectedLayout,
            { defaultSpringLength: 50, defaultElectricalCharge: 50 }),
          "undoManager.isEnabled": true
        });

    // install the LinkLabelDraggingTool as a "mouse move" tool
    myDiagram.toolManager.mouseMoveTools.insertAt(0, new LinkLabelOnPathDraggingTool());

    myDiagram.nodeTemplate =
      $(go.Node, go.Panel.Auto,
        { locationSpot: go.Spot.Center },
        $(go.Shape,
          {
            fill: "orange",  // default fill color
            portId: "",
            fromLinkable: true,
            fromSpot: go.Spot.AllSides,
            toLinkable: true,
            toSpot: go.Spot.AllSides,
            cursor: "pointer"
          },
          new go.Binding("fill", "color")),
        $(go.TextBlock,
          { margin: 10, font: "bold 12pt sans-serif" },
          new go.Binding("text"))
      );

    myDiagram.linkTemplate =
      $(go.Link,
        {
          routing: go.Link.AvoidsNodes,
          corner: 5,
          relinkableFrom: true,
          relinkableTo: true,
          reshapable: true,
          resegmentable: true
        },
        $(go.Shape),
        $(go.Shape, { toArrow: "OpenTriangle" }),
        $(go.Panel, "Auto",
          // mark this Panel as being a draggable label, and set default segment props
          { _isLinkLabel: true, segmentIndex: NaN, segmentFraction: .5 },
          $(go.Shape, { fill: "white" }),
          $(go.TextBlock, "?", { margin: 3 },
            new go.Binding("text", "color")),
          // remember any modified segment properties in the link data object
          new go.Binding("segmentFraction").makeTwoWay()
        )
      );

    // create a few nodes and links
    myDiagram.model = new go.GraphLinksModel([
      { key: 1, text: "one", color: "lightyellow" },
      { key: 2, text: "two", color: "brown" },
      { key: 3, text: "three", color: "green" },
      { key: 4, text: "four", color: "slateblue" },
      { key: 5, text: "five", color: "aquamarine" },
      { key: 6, text: "six", color: "lightgreen" },
      { key: 7, text: "seven" }
    ], [
        { from: 5, to: 6, color: "orange" },
        { from: 1, to: 2, color: "red" },
        { from: 1, to: 3, color: "blue" },
        { from: 1, to: 4, color: "goldenrod" },
        { from: 2, to: 5, color: "fuchsia" },
        { from: 3, to: 5, color: "green" },
        { from: 4, to: 5, color: "black" },
        { from: 6, to: 7 }
      ]);
  }
  window.addEventListener('DOMContentLoaded', init);
</script>

<div id="sample">
  <div id="myDiagramDiv" style="background-color: whitesmoke; border: solid 1px black; width: 100%; height: 600px"></div>
  <p>
    This sample demonstrates a custom Tool, LinkLabelOnPathDraggingTool, that allows the user to drag the label of a Link,
    but that keeps the label exactly on the path of the link.
    The tool is defined at <a href="LinkLabelOnPathDraggingTool.js">LinkLabelOnPathDraggingTool.js</a>.
  </p>
  <p>
    The label on the link can be any arbitrarily complex object.
    It is positioned by the <a>GraphObject.segmentIndex</a> and <a>GraphObject.segmentFraction</a> properties.
    The segmentIndex is set to NaN such that the whole link path acts as the segment, and the segmentFraction is set by the LinkLabelOnPathDraggingTool.
    A two-way data binding on segmentFraction automatically remembers any modified value on the link data object in the model.
  </p>
  <p>
    The tool is derived from a similar tool, <a href="LinkLabelDraggingTool.js">LinkLabelDraggingTool.js</a>,
    that allows the user to drag the label in any direction from the mid-point of the Link path.
  </p>
</div>
    </div>
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